DLR's Microwave and Radar Institute has been operating the F-SAR airborne SAR instrument since 2007. This contribution presents first the SAR imaging capabilities of the system followed by a discussion on recent developments in SAR signal processing using F-SAR data acquired in diverse special modes, each suitable for a specific application: large baseline, dual-frequency SAR interferometry for precise DEM generation, high resolution circular SAR imaging, advanced filtering and polarimetric change detection. The paper concludes with an outlook on future developments.